hello,
i'm in the search for new notebook up to price 700 eur, and i have a dilemma which one to buy.
so, I have few questions:
1st: is it more important to have more cpu cores or better gpu for faster rendering in archicad, artlantis, lumion etc.
2nd: some i7 cpu comes with only 2cores and others with 4 cores. is there significant difference?
3rd: how important is number of threads, because i saw AMD cpus with 4 cores and 4 threads, unlike the i7 which has 4 cores and 8 threads

1. As far as I know CPU is what is being used by most current rendering applications. Some applications start to appear that use the GPU or GPUs but there is only OctaneRender currently (that I know about) that is using GPUs:

2. A 4-core processor is better than a 2-core processor as it can handle 4 processing threads instead of 2.

3. Number of threads is what really counts. Intel has Hyperthreading which means that 1 physical core can run two processing threads in it. A 4-core 8-thread processor is better than a 4-core 4-thread processor. From the application's standpoint the former can process 8 threads for ArchiCAD or the rendering application, while the latter can process only 4 threads.
Even in Graphisoft's pages they say they recommend as many cores as possible:

In the last several releases Graphisoft has made great efforts to fully utilize multi-core processors and get as much performance out of them as possible. This is especially true with AC17 where they specifically say 4-8+ cores is really recommended. Previous they only said you should use multi-core processors, which means at least 2 cores.